Re: [O] Output result of source block to a file

[John Kitchin]

A similar approach as the last one should work, the problem I was having is that to print the binary string from python you have to decode it, and latin-1 seems close to right, but it puts a bunch of extra bytes in it that lead to a bad png file. I feel like this worked in Python2 with StringIO, but not in Python3 with BytesIO.

John

-----------------------------------
Professor John Kitchin 
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803

@johnkitchin
http://kitchingroup.cheme.cmu.edu

On Sat, Jun 8, 2019 at 6:52 AM Roger Mason <address@hidden> wrote:

Hello John,

John Kitchin <address@hidden> writes:

> you probably figured out the "import io" and "f = io..." line are not
> necessary here.

Indeed.

> I couldn't figure out a reasonable way to use :results graphics link
> that didn't result in repeating the filename more than desired. These
> also both work, but seem to both require repeating the filename twice.
>
> #+BEGIN_SRC python :results graphics link :var fname="test.png" :file "test.png"
> import matplotlib.pyplot as plt
>
> plt.plot([1, 2, 3, 1])
> plt.savefig(fname)
> #+END_SRC
>
> #+BEGIN_SRC python :results graphics link :file "test.png"
> import matplotlib.pyplot as plt
>
> plt.plot([1, 2, 3])
> plt.savefig("test.png")
> #+END_SRC
>
> Something like this should work, but there seem to be some extra bytes
> getting put in the png file from the decoding, and latin-1 is the only
> one I can get to work. If anyone knows how to get this to work, I am
> interested in seeing it!
>
> #+BEGIN_SRC python :results value :file "io.png"
> import matplotlib.pyplot as plt
> import io
> buf = io.BytesIO()
>
> plt.plot([1, 2, 3])
> plt.savefig(buf, format='png')
>
> s = buf.getvalue()
> return s.decode('latin-1')
> #+END_SRC
>
>
> In general though, all of these are much more work than using
> ob-ipython, which just puts images in the buffer for you.

I will investigate that, thanks for the tip.  I began this bit of work
using gnuplot for making x-y plots, but I find that gnuplot syntax gets
messy for anything but simple data.  I am not a particular fan
of python so I'm also looking into guile & racket for plotting.

Thanks for your help, it is much appreciated.

Roger